I want to pass the int i into the button onclick function for each list item. I expected the "clickItem" function will receive 0..2 for correspondig list item. But it come out that it always receive 3 as argument. It seems that the variable i in the clickItem(i) is not evaluated at the time of render of the for loop. I have tried changing it to "clickItem(@i)" but it is still the same. What should I do? (I am using blazor server side, .net core 3 preview 5)
@for (int i = 0; i < 3; i++)
{
<li> item @i <button onclick=@(() => clickItem(i))>Click</button> </li>
}
This is a classic C# problem with lambda's, but slightly new in the context of Blazor.
You need to make a copy of i
because otherwise "the lambda captures the loop variable". Capturing the copy is OK.
@for (int i = 0; i < 3; i++)
{
int localCopy = i;
<li>
item @i
<button onclick=@"() => clickItem(localCopy)">Click</button>
</li>
}
Note that this is an issue with for()
loops but not with foreach()
, and only on the right hand side of a =>
.